rough fwkw to rwkw conversion for 4wd

[Dzltec]

You cant have everything, they were able to be driven on the street, but were really comp cars, but we try to keep the off boost smoke down.


Andy

[madrolla68]

You cant have everything, they were able to be driven on the street, but were really comp cars, but we try to keep the off boost smoke down.


Andy

thats the hard bit with even moderate Hp cars, are you using Toyota FTE heads in those pumps???

[PGS 4WD]

What tyres were the figures obtained on and in what gear, ie what tyre speed? Recent testing I've done has shown that with one set of 37 inch tyres the power varied from 114 to 129 rwKw going from 2nd to 1:1 in an auto Nissan box(speed from 120 to 180klms/h), the difference being the tyre speed induced turbulance.
At the end of the day if you want to compare your vehicle to another you need same tyres, same rims, same diff, same diff ratio, same transmission in same gear with same tyre pressures and same amount of tyre wear(tread depth) and you'll come close to a true comparison, provided you use the same dyno and the atmospheric compensations are correct and the dyno callibrated the same.

I'm not saying that they aren't making that power just be aware that you can have the same engine power in a differnt vehicle and it may be slower or faster depending on a multitude of variables. Weigh the vehicles and do a 1/4 mile, the mile an hour calculator will tell you what is the most powerful based on mls per hour and mass over a set distance.

Or better still if your happy with your vehicles performance dont place to much emphasis on a figure. There are many cars with less power over a broader spread of the rpm range that will be quicker on or off road than big figure cars that have a narrow peaky powerband.

Joel

[Dzltec]

No we dont use those heads, they are an axial plunger, dont fit fit in ve pumps, we went through 8 diff h&r combinations to find one that works. Plus all the other bits that go with it. The final outcome is in my patrol, we have made a ve pump able to deliver 250cc fuel per cylinder at 1000 pump revs at 1000shots.

However push came to shove and the engine decided to let go, c'est la vie.

If some one can host a pic ill load up the dyno sheet.

Andy

[Dzltec]

Another quick note on driveline power consumption, my worker Matt swapped a gen 3 into gq wagon. In a vtss that the engine came from it made 226rwkw, in the gq it made 168 rwkw, no changes to the engine at all.


Andy

[me3@neuralfibre.com]

This is a kindof related article on parasitic losses and engine design compromises. Made me look at things differently. Nasa should have a clue what they are talking about.

http://www.prime-mover.org/Engines/GArt ... icle2.html

Paul[/url]

[PGS 4WD]

Another quick note on driveline power consumption, my worker Matt swapped a gen 3 into gq wagon. In a vtss that the engine came from it made 226rwkw, in the gq it made 168 rwkw, no changes to the engine at all.


Andy

Here here the truth, its refreshing to see Andy. It's good to see that there are others who deal in fact.

Joel

[nzdarin]

So 216rwkw on 35x11.5 Simex is pretty good then!
With the figures supplied a TD42 GQ loses about 45%.
Using that loss would mean my motor was producing about 390kw at 55% on the injectors, and the injectors can only handle that HP at about 80%. So obviously the loses aren't liner as there is no way my motor was producing anywhere near that HP as it was running rich with retarded timing, and restricted to 5000rpm. (instead of 7300)
I wish we could use it as it would once tuned my motor would have about 545kw when the reality is more like 440kw.
BUT upon saying that using a 30% lose gave us about what we expected so I does that mean the loses are constant hp loses rathr than a % so the more hp the less % loss? That sort of explains the result we got with my truck 2 weeks ago?
ie driving a given drive train will take a certain amount of hp and the auxilaries on a motor will also take a certain hp so regaurdless of how much hp is created the loss will be the same in hp not %. So by increasing the power of an engine at an engine speed then most of that power will end up at the wheels.

Argh i think people are starting to get it!!!!!

The losses calculated are for non-modded factory spec vehicles.If you want to know how much power your engine is making put it on a dyno that measures it dont guess.The drivetrain losses(excluding tyres) WILL not change no matter how much power you are making.If you make an extra 50Kw over std then ALL of the extra 50Kw gets to the wheels not a percentage of it.

Now if you were running simexs then my guess is you would have lost around 55Kw they are power sucking ***** fuka's.Now your figure of 216RwKw from a TD42???, how modded is it????.I would hazard a guess that that is 216FwKw from my experience but hey im happy to be shown otherwise.

Sorry I should have added that the TD42 has been removed and replaced with a turboed VH45 (Nissan 4.5 V8)

[me3@neuralfibre.com]

All these numbers are interesting and I don't disagree, but it's worthwhile re-thinking some of it. If you lose 20kw into tyres, that's 5kw / tyre, nearly all as heat. 5000w is one huge amount of heat for one tyre to dissapate....
Ditto for 10kw into a diff, that's going to be one smoking lot of oil.

Paul

[PGS 4WD]

What are you basing that on? As in my prior example with priming an oil system on a new engine, you will cause a cordless drill of 2-3 HP to stall at less than engine idle speed.

Ive done exactly that test on a 4wd Rangie and from old 35 11.5 Simex pedes to brand new is 20 kW at four wheels, thats 5kW in difference from old worn hard tyres to new soft with deeper tread.

10 kw dosen't necessarily all become heat either, what about noise?? No drivetrain component is quiet. And stored energy, until everything stops spinning and comes to rest(we usually turn this in to heat via the brakes).

5000W is a lot of heat in a light globe but not much in a 240 v motor. Take the example of a wheel balancer, most of these at a minimum are 15 amps single phase, the better ones 3 phase. Lets consider 15 amps at 240 v, thats 3600W to spin up a tyre to a relativly slow speed while off the ground, add some friction to that due to sidewall flex and alike and then spin it at 100 klms/h.
Dont forget that there are inertial and stored energy to be factored in. In accelerating the tyres on a ramp you now have stored energy, they don't just stop when you stop accelerating, they have stored energy until they reach zero speed again.
You will get a bigger figure on dyno that is true by checking the power at a set speed (not ramped) as it requires more energy to accelerate a mass than to maintain a speed, and the slower you ramp the vehicle the more power you will see at the wheels(disallowing for heat soak affecting engine performance) as rate of acceleration is lower F=MA (Force=Mass*Acceleration), A greater force is required to accelerate a set mass faster(Newtons Law). Energy is not destroyed or gained, it just changes state(except for Fission reators).

As for that amount of heat in a diff, that won't smoke oil, racecars do run diff oil coolers though, a diff has a much larger surface area to dissapate heat than a light globe and energy is being turned into heat and noise and some small amount stored.

Joel

[KiwiBacon]

All these numbers are interesting and I don't disagree, but it's worthwhile re-thinking some of it. If you lose 20kw into tyres, that's 5kw / tyre, nearly all as heat. 5000w is one huge amount of heat for one tyre to dissapate....
Ditto for 10kw into a diff, that's going to be one smoking lot of oil.

Paul

Consider that your radiator and exhaust are putting out about twice the power (as heat) that is going to the wheels.

100kw to the wheels, that's another 100 lost to the cooling system and another 100 lost through the exhaust.